The general construction of a stringed musical instrument is illustrated in FIG. 1, which shows an acoustic guitar. The guitar 1 consists of a body 2, to which is attached a neck 3. The guitar is provided with a plurality of strings 4-9; one end of each string is attached the body 2 and the other end of each string is attached to the end of the neck 3 distant from the body 2. Each string makes contact with a “saddle” 10 mounted on the body 2 and with a “nut” 11 mounted on the neck 3, and the maximum vibrating length of each string 4-9 is the length between the point where the string contacts the saddle and the point where the string contacts the “nut”. The “scale length” of each string is the maximum length of the string between the saddle 10 and the nut 11 that is free to vibrate. The strings are fastened to the guitar by fasteners 19 disposed beyond the nut and saddle.
The neck is provided with a fingerboard 12 on which is marked a plurality of frets 13. The fingerboard may be integral with the neck, in which case the frets 13 are marked on the upper surface of the neck, or the fingerboard may be a separate overlayer that is attached to the upper surface of the neck. A fret is essentially a line marked on the fingerboard to define a position for the player's finger that produces a desired musical tone. It is a requirement that each fret should allow reduction in the vibrating length of each string which is of the same proportion for each string. For example, on a certain instrument, the 12th fret may enable the vibrating length of each string of the instrument to be halved, compared to its maximum vibrating length. The nut may be considered as a zero fret. Tables exist that define the positions of the frets for a string having a standard maximum vibrating length, and the positions of the frets for strings having a different maximum vibrating length are found by scaling. Commonly, as shown in FIG. 1, the nut 11 is perpendicular to the centre-line of the instrument. Commonly, as also shown in FIG. 1, the saddle 10 is not exactly perpendicular to the centre-line of the instrument but is angled slightly to compensate for intonation errors between strings of different thickness. Thus each string has nominally the same scale length, with a small offset to compensate for intonation errors. For such an instrument, the frets 13 are perpendicular to the centre-line of the instrument.